The present invention relates to an exposure apparatus used for a semiconductor manufacturing process, and a projection exposure apparatus that projects and transfers a reticle pattern onto a silicon wafer. The present invention is suitable for an extreme ultraviolet (“EUV”) exposure apparatus that uses EUV light with a wavelength of about 13 to 14 nm as exposure light and a mirror optical system for projection exposure in vacuum.
A prior art example will be described with reference to FIGS. 12 and 13. 101 uses a YAG solid laser etc., serving as an excitation laser for exciting gasified, liquefied or atomized-gasified light-source material atoms into plasma for light emissions by irradiating a laser beam onto the (light-source emission) point on the material.
102 is a light-source emitting part that maintains an internal vacuum. A light source A (or 102A) is an actual emitting point in an exposure light source.
103 is a vacuum chamber that contains an exposure apparatus, and can maintain the vacuum state using a vacuum pump 104.
105 is an exposure light introducing part (or an illumination optical system) for introducing exposure light (or illumination light) from the light-source emitting part 102. The exposure light introducing part 105 includes mirrors A (or 105A) to D (or 105D), makes uniform and shapes the exposure ray, and illuminates a reflective original form (or reticle) 106A, which will be described below.
106 is a reticle stage, and its movable part is mounted with a reflective original form 106A that forms a pattern to be exposed.
107 is a reduction projection mirror optical system that reduces and projects an exposure pattern reflected from the original sequentially form through mirrors A (or 107A) to E (or 107E) onto a wafer 108A at a predefined reduction ratio.
108 is a position-controlled wafer stage for positioning a wafer 108A, as a Si substrate, into a predetermined exposure position so that the wafer stage can be moved along six axes directions, i.e., moved in XYZ directions, tilted about the XY axes, and rotated about the Z axis.
109 is a reticle stage support for supporting the reticle stage 105 on an apparatus installation floor. 110 is a projection optical system body for supporting the reduction projection mirror optical system 107 on the apparatus installation floor. 111 is a wafer stage support for supporting the wafer stage 108 on the apparatus installation floor.
The reticle stage 105, the reduction projection mirror optical system 107, and the wafer stage 108 are supported by the reticle stage support 109, the projection optical system body 110 and the wafer stage support 111, respectively. These include means (not shown) for measuring relative positions so as to continuously maintain their predetermined configuration.
A mount (not shown) for violation isolation from the apparatus installation floor is provided on the reticle stage support 109, the projection system body 110, and the wafer stage 111.
112 is a reticle stocker that includes a storage container that temporarily stores, in an airtight condition, plural original forms supplied from the outside to the inside of the exposure apparatus and suitable for different exposure conditions and patterns.
113 is a reticle changer for selecting and feeding a reticle out of the reticle stocker 112.
114 is a reticle alignment unit that includes a rotary hand that can travel along the XYZ axis directions and can rotate about the Z axis. The reticle alignment unit 114 receives the original form 106A from the reticle changer 113, rotates it by 180°, and feeds it to a reticle alignment scope 115 provided at the end of the reticle stage 106 for fine movements of the original form 106A rotating about the XYZ-axes and aligns the original form 106A with an alignment mark 115A provided on the reduction projection mirror optical system 107. The aligned original form 106A is chucked on the reticle stage 106.
116 is a wafer stocker that includes a storage container for temporarily storing plural wafers 108A from the outside to the inside of the apparatus. 117 is a wafer feed robot for selecting a wafer 108A to be exposed, from the wafer stocker 116, and feeds it to a wafer mechanical pre-alignment temperature controller 118 that roughly adjusts feeding of the wafer in the rotational direction and controls the wafer temperature within controlled temperature in the exposure apparatus.
119 is a wafer feed hand that feeds the wafer 108A that has been aligned and temperature-controlled by the wafer mechanical pre-alignment temperature controller 118 to the wafer stage 108.
120 and 121 are gate valves.as mechanisms for opening and closing a gate for supplying the reticle and wafer from the outside of the apparatus. 122 is also a gate valve that uses a diaphragm to separate spaces among the wafer stocker 116, the wafer mechanical pre-alignment temperature controller 118, and the exposure in the apparatus. The gate valve 122 opens and closes only when feeding the wafer 108A in and out of the apparatus.
Such a separation using the diaphragm can minimize a capacity to be temporarily released to the air when the wafer 108A is fed in from the outside of and fed out of the apparatus, and quickly form a vacuum equilibrium state.
However, when the conventionally structured exposure apparatus positions and fixes the mirrors A (or 107A) to E (107E) relative to the mirror barrel 107F as shown in FIG. 13, carbon, such as the trace of CxHy (hydrocarbon), adheres to and clouds up a surface of the mirror.
When the mirror surface is clouded up, the mirror's reflectance to the EUV light disadvantageously lowers and becomes non-uniform according to (light-reflecting) locations on the mirrors.
When this problem occurs in the illumination optical system in the exposure apparatus, the exposure apparatus suffers from significant problems: The light for illuminating the reticle has lowered intensity or cannot illuminate the reticle uniformly (or has the non-uniform intensity).
When this problem occurs in the illumination optical system in the exposure apparatus, the exposure dose that reaches the wafer lowers, resulting in a long exposure time and lowered throughput. When hydrocarbon and the like adhere to the mirror surface, the mirror's surface shape changes and the imaging performance of the projection optical system deteriorates.
Thus, when hydrocarbon and the like adhere to the mirror surface, the mirror should be exchanged. However, it is not easy to exchange the mirror in the conventional exposure apparatus.